Understanding the oxygen evolution activity trend in Co2Fe LDH-N doped graphene hybrids

Abstract

We report the electrocatalytic activity of nanosized Co2Fe-layered double hydroxide (LDH) on nitrogen doped graphene (NG) hybrid materials toward oxygen evolution reaction (OER). An enhanced activity trend was observed with increase in amount of LDH in the hybrid. The highest activity in terms of onset potential (1.48 V), Ej=10 (1.54 V), and Tafel slope (61 mV/dec) was observed for 75 wt% LDH, which is better than pristine LDH and the state of art RuO2. The origin of activity enhancement in the hybrids was correlated with different electrochemical parameters and physical properties of the constituents. In earlier reports, generally the decrease in charge transfer resistance (RCT) at the electrode electrolyte interface was correlated with increase in OER activity. However, in case of LDH-NG hybrids, a completely opposite trend was observed. The TGA and XRD results showed that higher amount of LDH loading inhibits the NG stacking. The hydrophilic property of LDH, uniform distribution of LDH on NG without agglomeration, and inhibition of NG stacking were proposed to be the reason behind the observed trend in activity.